code: def test_2by2(self, Source):
      source = Source()
  
      e_img, _, e_extent = source.combined(-1, 50, 2, 1)
      assert e_extent == (-1, 1, 50, 51)
      imgs = [
          source.single_tile(-1, 50)[0],
          source.single_tile(0, 50)[0],
      ]
      assert_array_equal(np.hstack(imgs), e_img)
  
file_path: cartopy/lib/cartopy/tests/io/test_srtm.py
imports: import numpy
  from numpy.testing import assert_array_equal
  import pytest
  import cartopy.crs
  import cartopy.io.srtm
  from .test_downloaders import download_to_temp
label_desc: Use image node_id 2 for calling the TestSRTMSource__combined obj's underlying member method code with example usage: obj.test_2by2(Source) without return types